Holder for cartridge enclosed protectors for electric circuits



Feb. 2, 1954 DUERKQB 2,668,215

HOLDER FOR CARTRIDGE ENCLOSED PROTECTORS FOR ELECTRIC CIRCUITS Filed Aug. 7, 1948 2 Sheets-Sheet l f VVENTOR MANFR DUE'RKOB ORA/E) 1954 M, F. DUERKOB 2,668,215

HOLDER FOR CARTRIDGE ENCLOSED PROTECTORS FOR ELECTRIC CIRCUITS 2 Sheets-Sheet 2 Filed Aug. 7, 1948 [A] VENTOR BYMANFRED DUERKOB Patented Feb. 2, 1954 .1 I: .'.l

UNITED STATES PATENT OFFICE HOLDER FDR CARTRIDGE ENCLOSED PRO- EECTORS FOR ELECTRIC CIRCUITS Manfred F. Duerkob, St. Louis, Mo., assignor to McGraw Electric Company, Elgin, 111., a corporation of Delaware Application August '7, 19%, Serial No. 43,035

4 Claims. (01. 200--129) This invention relates to improvements in holders for cartridge enclosed protectors for electrio circuits. More particularly, this invention relates to improvements in devices that hold and support cartridge enclosed protectors for electric circuits.

It is therefore an object of the present invention to provide an improved. device for holding and supporting cartridge enclosed protectors for electric circuits.

In the use of cartridge enclosed protectors for electric circuits it is oftentimes desirable to pro vide. a number of clips or mounting blocks in which the protectors for electric circuits are mounted and secured. In such instances, a number of the blocks or clips are mounted adjacent each other, and the circuit protectors supported thereby. In other instances, it is desirable to provide individual devices for holding and supporting each of the cartridge enclosed protectors for electric circuits. Where the cartridge enclosed protectors for electric circuits are electric fuses of generally cylindrical form, the devices for holding and supporting the protectors for electric circuits frequently take the form of elongated hollow structures that can be supported in a panel or other support and that can have leads or wires connected to them. A number of holders of this general type have been proposed and built, but none of them has been truly satisfactory. The present invention provides a device, for holding and supporting cartridge enclosed protectors for electric circuits, which overcomes many of the deficiencies of prior art holders, and which is a marked improvement there- CV81.

Prior holders for cartridge enclosed electric fuses had projecting contacts or terminals to which leads or wires could be soldered or other wise secured. Such projecting contacts or ter minals, and the leads or Wires secured thereto, were constantly exposed to accidental contact by other leads or wires or by sharp metal points; and any such accidental contact might bypass the fuse and lose the protection normally afforded by the fuse, might needlessly cause the fuse to open, or might interconnect two normally independent circuits with undesired results. The present invention obviates such accidental contact by providing a holder for cartridge enclosed electric fuses wherein all of the contacts or tor minals are disposed wholly within the holder and wherein no live parts are exposed. With such an arrangement, the insulation on the leads or wires extends into the holder; and the leads being secured to the contacts within the holder. all external portions of the holder and lead or wires are covered with insulation. It is therefore an object of the present invention to pro vide a holder for cartridge enclosed electric fuses wherein all of the contacts are disposed wholly Within the holder and wherein no live parts are exposed.

' In certain prior holders for cartridge enclosed electric fuses, it was felt desirable to provide openings which extended from the exterior to the interior of the holders and thus extended to points adjacent the electric fuses disposed within those holders. Such openings are undesirable because they can permit accidental contact of a wire or a sharp point of metal with the cartridge enclosed electric fuse. The present invention obviates any such accidental contact by providing a holder for cartridge enclosed electric fuses wherein all openings or passages from the exterior to the interior of the holder are either closed or bafiied when the holder is assembled. It is therefore an object of the present invention to provide a holder for cartridge enclosed electric fuses wherein all openings from the exterior to the interior of the holder are closed or bafiled when the holder is assembled.

The holder for cartridge enclosed fuses provided by the present invention has contacts to engage the terminals of the electric fuse disposed within the holder. One of those contacts i disposed adjacent the innermost end of the cavity within the holder provided by the present invention; and that contact is of dish-shaped-configuration, having a relatively fiat center portion and an upstanding rim. The upstanding rim will engage the end face of the terminal of the cartridge enclosed electric fuse, while the relatively fiat center portion will normally be spaced a short distance away from the end face of the fuse terminal. Such an arrangement enables the contact to attain intimate electrical engagement with the terminal of the cartridge enclosed electric fuse even though the fusible link of that fuse is secured to that terminal by an irregularly shaped mass of solder on the exterior of the end face of that terminal; the space between the center portion of the contact and th end face of that terminal accommodating the mass of solder and thus permitting the upstanding rim to engage the end face of the terminal. The upstanding rim will thus provide line contact rather than point contact between the innermost contact of the holder and the one terminal of the fuse; such e contact guaranteeing a good electrical connection between the fuse and that contact, even though the mechanic may have gotten some dirt or grease on the terminal of the fuse while inserting the fuse in the holder. It is therefore an object of the present invention to provide a holder for cartridge enclosed electric fuses with a contact that has a relatively flat center portion and an upstanding rim.

The leads or wires connected to the contacts of the fuse holder of the present invention are encased within the insulation, which forms part of that fuse holder, for considerable distances. With such an arrangement, any deterioration in the value of the insulationhnth'e leads or wires, due to soldering or any excessive'strippingof the leads or wires preparatory to soldering, is not objectionable since any insufficiently insulated or bare portions of the wires or leads will be wholly confined within the insulation of the holder. It is therefore an object of the present invention to .providea fuse holder, largely made of insulating material, that receives the insulation on the leadsorwires extendingto thecontacts disposedwithin the fuse holder.

In prior cartridge enclosed fuse holders the various parts of the fuse holder had to be assembled very carefully and 'inai'ntain'ed in assembled relation during manufacture. With the present invention, the elements that are positi'o'ned'in the holder and that serve to support the wires or leads are individually 'inserta'o'le into the holder atter the holder has been formed.

Wherecartridge enclosed fuse holder's secured to an 'instruinent panel or other portion 'ofa land, air 'orsea vehicle, it is oftentimes dif- 'flcult to rcach into the necessarily crowded-areas behind the-instrumentpanel andsolder or otherwise secure "the leads or wires to the terminals or contacts of the fuse holders. This problem is obviated by the-present invention by providing 'long 'leads as part of the fuse holder. The profleeting ends of these leads extend outwardly from the fuse holder of the present "invention and can be moved a considerable distance away from the instrument panel 'for connection to wires extending from the apparatus to be protected by the fuse. In such instances, there is no crowding in and around the areas'where the "electrical'connections are to be made; and thus the presentinvention simplifies the securement of the leads of the fuse'holder to the wires exf tendingfrom the'appa'ratus to be protected. It is therefore an object of the present invention to provide a fuse holder with relatively long leads for connection to the apparatus to be protected.

Where fuse holders are secured to aniristru- I "the fuse holder in a direction parallelto'the axis of "the fuse holder. It is therefore an object of "the present invention to provide a fuse holder wherein the leads or wires extend into the fuse holder in a direction parallel to "the axis of the fuse holder.

The fuse holder of the present invention has a'stationary'contact that can be madeby punching'itfrom a flat sheet of metal. Such an element has a central opening to receive t e 1 156 manufacture of the fuse holder of the present invention. In addition, that contact has an opening throughwhich the lead or wire to be connected to that contact may be passed; and such opening facilitates the assembling and soldering of the lead or wire to that contact.

It is therefore an object of the present invention to provide =a stationary contact which can be punched from a fiat sheet of metal, which has an opening to receive the lead or wire, which has anchoring projections to extend into recesses in the fuse holder to maintain it in position, and has projec'tions to limit rotation of th'e'movab'le contact carried "by the detachable closure of the fuse holder.

Other and further objects and advantagesof the present invention should become apparent from an examination of the drawing and ac company'ing description.

In the drawing and accompanying description 2. preferred embodiment of the present invention is shown and described but it is to be understood that the drawing and accompanying description are for the purposes of illustration'only and-(lo not limit the invention and that the invention will "be defined by the appended claims.

In the drawing,

Fig. 1 is a cross sectional, side view'of a holder for cartridge enclosed protectors "for e1ectric'circults, and it shows that holder assembled -on a panel'with a'protector for electric circuits confined therein,

"Fig.2 isa cross sectional, side view of 'the'hous ing of the holder of Fig. 1,

Fig. 3 is an end view of the housing-shown in Fig. '2,'and it shows the l'arger-end-of that housing.

Fig. 4 is an end view of the housing shown in Fig. 2, and it shows the smaller end of that'hous- Fig. 5 is aperspective view of one contact of the holder shown inFig. 1,

Fig. 6 is an end view of the stationary contact used with theholder of Fig. 1,

'Fig. 71s aplan view of the contact .of Fig. 6.

Fig. 8 is aside view of the contact of Fig. 6, and it shows that contact assembled with a lead or wire,

Fig.9 is a perspective view of a bent sleeve used to hold the holder of Fig. 1 in assembled relation with an instrument panel,

Fig. 10 is a somewhatreduced, perspective view of the detachableclosure of the holder shown in Fig. l, and

Fig. 11 is an end view of the housing-of Figs. 2-4, and it shows the contact of Figs. 6-8 as sembled with that housing.

Referring to the drawing in detail, .thenumeral 20 generally denotesa body-or housing that is a part of a holder for cartridge enclosed =protectors for electric circuits made in accordance with the principles and teachings of the present inventi'on. As .disclosed in the drawing, the'hous- 'ing 20 is aunitary piece of insulating material;

the housing '29 is highly desirable because it 5, permits inexpensive but accurate formation of the housing 20. The housing 20 has a cylindrical body portion 22 projecting from the rear thereof, and that portion has a bore 24 of uniform diameter therein. The left hand end of the cylindrical body portion 22 is closed by a wall 26, and that wall has an opening 28 therethrough. The opening 28 is concentric with the bore 24 in the cylindrical body portion 22. The bore 24 extends into the large diameter cylindrical body portion 30 of the housing 20, which portion is concentric with and contiguous to the cylindrical body portion 22. A cylindrical body portion 32 is formed as a part of the housing 28; and that portion is eccentric to the body portions 22 and 3%. A tapered section 34 is made integral with the cylindrical body portions 22 and 30; and that tapered section extends between the body portions 22 and 30, and it also merges with the left hand end of body portion 32. A flange 35 is provided for the large end of the housing 20, and that flange projects radially outwardly from the cylindrical body portion 30. The flange 35 is concentric with body portions 22 and 30, and it merges with the eccentric cylindrical portion 32 of the housing 20.

A recess 36 is provided in the cylindrical body portion 30 and that recess is concentric with and contiguous with the bore 24, but it has a larger diameter than that bore. A second recess 38 is provided in the flange 35, and that recess is concentric with and contiguous with the bore 2e and recess 36, and it has a larger diameter than that bore and that recess. The bore 24 and the recesses 36 and as form a cavity within the housing 23 to receive a cartridge enclosed electric fuse. A pair of oppositely disposed recesses 40 are formed in the side walls of the recess 38, and the recesses 48 extend into the flange 35.

' The offset body portion 32 has a uniform diameter bore 42 therein, and that bore extends into theflange 35 and merges with the recess 38. Consequently, the right hand end of the bore 32 merges with and opens into the cavity that receives the cartridge enclosed electric fuse. The bores 24 and 42, and the recesses 36, 33 and lii can all be made in the same operation in which the housing 20 is itself made; and such an arrangement minimizes the cost of making housing 20. It will be noted that, as molded, the housing 2b can be entirely free of embedded metal components. This not only obviates the cost of the metal, but also simplifies the manufacture of housing 20.

A helical spring 44 is positioned within the bore 24, and that spring is dimensioned so it can be compressed without binding or jamming in the bore 24. The inner diameter of the spring 44 is large enough so the spring can surround the rearwardly extending sleeve on the inner contact 46 of the holder. That sleeve receives the stripped end of a lead or wire 43; and the end of lead 4-8 can be permanently secured to the contact 46, as by crimping the end of the sleeve onto the end of that lead, by soldering that end of the lead into the sleeve, or by any other suitable method. The opening 28 in the wall 26 of the housing 20 is preferably dimensioned so the insulation of the lead 48 substantially fills that opening, thus tending to prevent the introduction of a wire or piece of metal into the opening 28. However, the diameter of lead 48 must be small enough, relative to the opening 28, to permit movement of lead 48 relative to that opening.

The contact 46 has a dish-shaped configuraably smaller than, the terminal 6. tion; having a relatively fiat center portion 43 and also having an upstanding rim 45. The rim 45 extends a slight distance ahead of the center portion 43 of contact 46, and it will bear against the end face of the terminal of a fuse disposed within the holder, even though an irregularly shaped mass of solder is on that end face. In the absence of this dish-shaped configuration of contact 46, an irregularly shaped mass of solder on the end face of the terminal of the fuse might limit the engagement between the contact and the fuse terminal to mere point contact. With the dish-shaped configuration of contact it, however, the space between the center portion of the contact and the end face of the fuse terminal will accommodate any solder mass on the terminal and permit the rim to seat firmly against that terminal. This provides line contact betweenv the terminal of the fuse and the con tact as; and this line contact will assure a good electrical connection even through the mechanic in inserting the fuse happened to get dirt or grease onto its terminals. The contact 46 has a diameter that is no greater than, and is preferof the fuse, whereby the contact engages the end face of the fuse terminal and does not act as a cup to grip and hold the fuse. The contact 48 will reciprocate within the bore 24, but it is confined against radial movement; thus the contact as is of the semi-fixed type.

The numeral 5d generally denotes a stationarycontact which is positioned within the housing 20. That contact has an opening 52 at one side thereof to receive a lead or wire 58, it has anchoring projections 56 extending outwardly from the sides thereof, it has a notch 5G to receiv a projection es on the movable contact 64 carried by detachable closure 62 of the holder, it has a gap 58 between the free ends of the sides thereof to receive the other projection 69 on the movable contact '63, and it has depending projections 55! which normally limit rotation of projections 60.

The contact 64 may be punched out of a flat sheet of metal; and in that case it will have axially extending slits 6i. However, contact 64 can be made by other methods. outwardly extending projections 60 are formed on the outer end of contact 64; and axially extending ridges 63 are formed on the sides of that contact to.

assist in securing that contact within closure t2 and to make that contact acircular. The cavity in contact 64 is large enough to receive a fuse terminal readily; but bent portions 65, spaced from the inner end of the cavity a distance greater than the length of that terminal, are spaced apart a distance slightly smaller than the diameter of that terminal. These bent portions normally do not engage the fuse terminal, but instead lie behind the terminal and resist accidental separation of fuse and contact. A shoulder 66 on closure 62 has a diameter smaller than that of recess 38. Shoulder lit projects into recess 38 when the closure E2 is assembled with housing 2t, and it cooperates with the walls of recess 38 to obviate a straight-line path from the exterior to the interior of the holder.

The stationary contact 50 can be made by punching it from a flat sheet of metal; it is initially provided with a circular central opening and it preferably is made with an outer diameter slightly less than the diameter of recess 38. It I is then bent until the gap 58 is closed, it is inserted in the recess 38 so the anchoring projections 54 register with recesses 40 in housing 20,

and thenthe sidesof. the contactarespreadapart toforce projectionst l into recesses so. However, the central opening is not rendered circular again; instead, the midpoints of the sides of corn tact'ts are spaced apart a distance smaller than the original diameter of the central opening. This. distance is smaller than the distance be tween ridges 53 on contact it although the diameter. of the original central opening in the contact at Was greater than the distance between ridges 55.

If. desired, contact-.55. could bemade of springy metal, momentarily bent until the distance betweenthe outer. edges of projections Ed was less than the diameter of recess 38, slipped into recess 8, and. then released so the projecticnsfit would. enter recesses to; and also. if. desired, the contact couldbe. made. with a slit rather. than the gap 58, whereby the distance between: the anchoring projections i initially lessthan the diameter of recess 38. In the latter two arrangements, the step of closin gap as can be eliminated; and where? the contact is-made with aslitrather than gap 58, the contactneed only be inserted in recesslfil and expanded. Once placed inthe positionlshown in Fig; 11, the contactttwill remain inthat position and be locked in. assembled relationwithhousing'it. Intha't positionthe semicircularportionof contact 5 which is adjacent opening 52, will extend into the bore. l2..where that bore merges with recess 38.

Prior tothetimethe contact so is introduced into: and. locked in. the recess 38, the end of a lead. fit will be passed through opening 52 in contact 5t; and that end will be securedto. contact fit, as by solder i0. Thereafter the free end oflead 63 will be threaded. throughbore 32, andv contact to will be seated and locked in recess 38. Solder ill will makes. good electrical connection between lead c8 and. contact. EU, and it will also enable contactiiil to support lead 68. 50 will serve to releasably connect lead with movable contact s4 on closure 62.

When the housing 2!! hasbecn equipped with innermost. contact 4E, helical spring as; lead it, stationary contact 56, and lead 68, it is-readyfor insertion in" an instrument panel 2. This panel maybe apart of aland, seaor air vehicle or it maybe-part1 of a stationary structure. To iacilitate thesecurement'- of the housing 2o to the in strument. panel either: a lceyhole shaped opening or a circular opening should be made in that: panel. The keyhole-shaped opening is ole sirable because it cooperateswith the shape of housing 28 toresistrotation of the holder. The keyhole-shaped openingshould have a large diameter section to accommodate body portion-3t and should have a small diameter section to accommodate the eccentric body portion 32; and

the circular opening should have a diameter slightlylarger than the distance between the top of body portion 3t and the bottom of body portion 32. The housing 26 will be held in assembled relation with the panel "i2 by a split sleeve it which is positionedbetween the outer periphery of the body portion 33- and the inner periphery of the opening. The sleeve i4 isprefera'bly made ofresilient metal, as for example spring steel; and it has notches "H- and projections portions of the sleeve i i adjacent thenotehes H are bent inwardly, and the projections dil'are bent outwardly; and as a result the sleeve it can simultaneously bite into the materialsof which thebody portion Sil and the iustrumentpanel "32 are" made; or can biteinto-the body-portion as Contact The and can project beyond the far side-ofv the panel: and prevent the removal ofthe'sleeve andhous-- ing. With this arrangement, simple and quick installation of the holder is possible; and the holder will be held against accidental dislodge ment. It will be noted that the sleeve "N isnot a complete cylinder, but instead is only about: seven eighths of a cylinder. This enables" the sleeve to be used without extending completely under the eccentric body portion 32 Thus. the sleeve i can be used to confine the circularright hand portion of the housing Once-the: housing 29 and sleeve i l have been placed inposition, they will resist all ordinary attempts: to"- remove them.

In use, the housing together with innermost contact it, stationary contact 56, spring.44,=, and leads 58 and at, is permanently mounted in theopening in the instrument panel i2. Thereafter a fuse 8B isinserted in the cavity of contact 51; closure and thefuse carried thereby are movedadjacent the housing 2%, the projections 60 of: contact are aligned with the gap and'the notch 56 of contact and the closure 62 is moved toward the recess until the shoulder 66 enters the recess and untilthe: projections cc pass through the gap and notch 55 of con tact 5t. To do this, only a slight pressure: on closure G2 is needed to compress thehelica-l spring: M. Once the projections 68 havepassed'through' the gap and the notch 56, therclosure-ifl can be: rotated about ninety degrees and then released; Thereupon the compressed spring' l i will expand; forcing the rim of disl1-shaped contact it into intimate engagement with one terminal of fuse to, forcing the other terminal of fuse so into in tirnate engagement with contact {5. and forcing projections oi contact 5'4 into intimate en'- gagement with the stationary contact 56. Thus the spring i l directly assists in maintaining intirnate electrical engagement between fuse 8t and" the contacts and 6 3, and in maintainingin' timate electrical engagement between contacts of] and 6 When the closure 82 is rotated, the ridges tl3are' moved into engagement with the midpoints of the sides of contact 58, thus spreading those sides apart still further. Those sides will tend to res turn to position and will thus provide a sizea-ble: contact pressure ridges 83; thus providing intimate and completely adequate engagement between contacts t l and Such electricalemgagement obviates the uncertain engagement, high contact resistance, and heating exp'erieric'ecl in former fuse holders.

In turning the closure 62, but little care-need be used by the operator because movement of the projections "Gil will normally be limited by the projections on contact thus preventing accidental separation oi closure 62' and housing: 2%. Intentional separation of. closure and housing is easily effected by pressingithe closure 52 toward the housing 263 While rotating the projections 6t; into register with the gap Mand the notch of contact 'lhereaiter, mererelease of the pressure on the closure 62' will-en able the helical spring i i to move the. closure 62 out of engagement with the contact such time, the closure be removedito facilitate inspection or replacement of the fuse til.

All openings housing are substantiall'y closed or bafiled henthe holder is assembled; This is very desi aole because it 007181133 the" existence-oi any straight inepathfronrtheexterior to the interior of the holder, thusavoidin'gany accidental contact with wires, leads, or pieces of metal, and also excluding dirt, dust and foreign matter. It should also be noted that the leads 48 and 68 are insulated, and that the insulation on those leads extends sufiiciently far into the fuse holder so the ends of the leads 48 and 68 are encased both by their own insulation and by the insulation forming the bores 24 and 42. This provides an unusually safe construction.

The leads 48 and 68 project coaxially from the rear of the housing 28, and they are parallel to the axis of the housing but of course they can easily be bent in any desired manner outside of the housing 20. These leads may extend away from the crowded and congested conditions immediately behind the instrument panel 12, and, since the leads will preferably be six or more inches in length, they can be connected to wires extending from the apparatus to be protected at a. distance from the instrument panel. In this way, installation is made simple and safe; and there is but little danger of accidental contact with other leads during installation. In addition, there is no live part exposed on the surface of the fuse holder when it is assembled; everything exposed being of insulating material. As a result, an extremely safe construction is provided.

Whereas a preferred embodiment of the present invention has been shown and described, it should be obvious to those skilled in the art that various changes may be made in the form of the invention without affecting the scope thereof.

What I claim is:

'l. A holder for cartridge enclosed protectors for electric circuits that comprises a two-part elongated body that is of insulation material throughout the length thereof, one of said parts having a portion formed as an imperforate continuous wall to define a central bore and having a second portion formed as a wall to define a second bore of reduced cross-section, said bores being coaxial and contiguous and defining a continuous bore adapted to receive a cartridge enclosed protector for electric circuits, said second portion having a cross-section smaller than the cross section of the first said portion whereby said first portion extends radially outwardly beyond said second portion to define a shoulder, said second portion being insertable through an opening in a panel and said shoulder being registerable with the portions of said panel that define said opening in said panel, said second portion having a wall at the end thereof which is spaced from the first said portion, said end wall having an opening therethrough of smaller cross section than the crosssection of said second bore, a contact in said continuous bore adjacent said end wall in register with said opening in said end wall to receive one end of said cartridge enclosed protector for electric circuits, a second contact disposed within said continuous bore intermediate the ends thereof and spaced from the first said contact, said second contact having arms that extend circumferentially of said continuous bor and terminate short of each other to define a gap, a notch in said second contact, a recess in said first part that is contiguous with said continuous bore, a portion of said second contact extending into said recess and being electrically connected to a conductor that extends co-axially with said continuous bore, the other of said parts carrying a third contact, said third contact receiving the other end circuits and having circumferentially spaced projections thereon that selectively extend inwardly of and underli and engage said arms and thereby limit movement of said third contact outwardly of said continuous bore and electrically connect said second and third contacts, one of said projections on said third contact being registerable with and passing through said gap and another of said projections on said third contact being registerable with and passing through said notch.

2. A holder for cartridge enclosed protectors for electric circuits as claimed in claim 1 wherein said third contact is a hollow cylinder wherein axially extending slits are formed in the wall of said cylinder, wherein axially extending ridges are formed in the wall of said cylinder and are in alignment with said projections and project radially outwardly and wherein said arms are locally distortable by said ridges to permit rotation of said third contact relative to said second contact and to establish an electrical connection of low resistance between said second and said third contacts.

3. A holder for cartridge enclosed protectors for electric circuits that comprises a two-part elongated body that is of insulation material throughout the length thereof, one of said parts having a portion formed as an imperforate continuous wall to define a central bore and having a second portion formed as a wall to define a second bore of reduced cross-section, said bores being coaxial and contiguous and defining a continuous bore adapted to receive a cartridge enclosed protector for electric circuits, said second portion having a cross-section smaller than the cross-section of the first said portion whereby said first portion extends radially outwardly beyond said second portion to define a shoulder, said second portion being insertable through an opening in a panel and said shoulder being registerable with the portions of said panel that define said opening in said panel, said second portion having a wall at the end thereof which is spaced from the first said portion, said end wall having an opening therethrough of smaller cross-section than the crosssection of said second bore, a contact in said continuous bore adjacent said end wall in register with said opening in said end wall to receive one end of said cartridge enclosed protector for electric circuits, a second contact disposed within said continuous bore intermediate the ends of said continuous bore, a notch in said second contact and a portion of th periphery of said second con tact that is in register with said notch and that projects radially outwardly away from said notch, said second contact having arms that extend circumferentially of said continuous bore and away from said notch and away from said projecting portion of the periphery of said second contact, said arms terminating short of each other to de fine a gap, a recess in said body that is contiguous with said continuous bore to receive and confine said outwardly projecting portion of the periph cry of said second contact and thereby to resist rotation of said second contact, a third contact in th form of a hollow cylinder which is carried by the other part of the holder and which has a projection thereon which extends radially outwardly beyond the surface of said hollow cylinder, said third contact being adapted to encircle the other end of said cartridge enclosed protector for electric circuits and to hold said protector so the said one end thereof can be introduced into said continuous bore and moved between said of said cartridge enclosed protector for electric arms of said second contact and into engagement aces-ma with thefirst said contact; said projection on" said third contact being registerahzle" withand:

passing throughsaid can, said third contact being' rotatable relative to said second Contact to place-said: projection in register with said arms of said second contact and thereby prevent. accidentalrseparation of said -second and said third contacts, said third contact conducting: current from said secondcontactto said other end of said.

protector.

4. A'- holder for cartridge enclosed protectors for electric circuits: that comprises a two-part elongatedbody'thatis of insulation materialthrougr out the lengthth'ereofi one of saidipartsxh'aving"a. portion formed as an imperlorate continuonsxwall;

todefine: a. central boreand having a 5800111111301"- tion formed as a Wall to define a second: bore of reduced cross-section, said bores being coaxial. and; contiguous and defining a continuousboreadapted to receive cartridge enclosed. protector;

for electricicircuits, said second portionliaving'ia cross-section smaller than the cross: section of the first said portion whereby said first portion extends radially outwardly beyond saidv second portion. to define a shoulder. said second. portion being insertable throughan. opening in a panel.

and said' shoulder being registerabl'e with. the portions of saidpanelthat definesaidxopening in said panel, said second portion havingv a wall" at the end: thereof whichis spaced. from thefirst. said portion; said" end: wallhaving an openingtherethrough of. smaller cross-section than thecrosssection of: said' second bore, a contact in said continuous. bore adjacent said end" wall in register with said opening in said end wall to; receive one end of said cartridge enclosed protector. for electric circuits, a second contactdisposed within'said continuous bore intermediate the ends of said continuousdoore; a notch in said second contact. said second contact having: arms'that extend circumferentially of said continuous bore and away from said notch and terminate short of each otherto define a gap; a recessin said body-that is contiguouswith said continuous bore, a portion of said secondcontact extending, into said recess and being" electrically connected: to a conductor,

a third contact in the' form of a hollow cylinder which is carried by the other part of said holder-- and which has circumierentially spaced projectionsthereon that extend radially outwardly be gap,- another of said projections being register-able with and passing through said notch, said third contact being rotatable relative to said second contact to place said projections in register with said arms of said second contact and thereby prevent accidental separation of said second and said.- third cont: said third contact conducting current from said second contact to saidother end 01 said protector;

MANFRED F. DUl'JR-KQB;

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